King Ash Bay 2012 - 307  Visitors to King Ash Bay 2012- 3,500 - 5,5008 (Not Including Cabins, Lodge and Houseboats)

McArthur River Monitoring

Bill Sawynok, Wendi Parsons and John Platten

Infofish Australia, PO Box 9793, Frenchville, Queensland 4701

McArthur River Monitoring page 1 Published by Infofish Australia

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Cover designed by Creative Avenue Rockhampton

TABLE OF CONTENTS

McArthur River Monitoring page 2 ACKNOWLEDGEMENTS ...... 5 SUMMARY ...... 6 1. BACKGROUND ...... 10 2. PROJECT OBJECTIVES...... 10 3. PROJECT AREA...... 11 4. FISHING CHARACTERISTICS...... 11 5. WHAT INFLUENCES FISHING?...... 13 6. WHO GOES FISHING? ...... 16 7. WHEN DO THE3Y GO FISHING?...... 17 8. WHERE DO THEY GO FISHING?...... 18 9. WHAT IS A TYPICAL FISHING TRIP?...... 20 10. HOW MANY FISHING TRIPS?...... 22 11. WHAT IS THE CATCH?...... 27 12. FISHING COMPETITIONS ...... 31 13. BARRAMUNDI TAGGING ...... 32 14. BARRAMUNDI GROWTH...... 37 15. BARRAMUNDI MOVEMENT...... 38 16. BARRAMUNDI SIZES ...... 41 17. BARRAMUNDI RECRUITMENT ...... 43 18. ELECTROFISHING SURVEYS...... 45 19. GOLDEN SNAPPER TAGGING...... 47 20. COMPARISIONS WITH OTHER RIVERS...... 50 21. DISCUSSION ...... 52 22. COCLUSIONS ...... 54 23. APPENDIX 1...... 55 24. APPENDIX 2...... 56

FIGURES

Figure 1: McArthur River project area...... 11 Figure 2: Commercial netting closures adjacent to the McArthur River...... 12 Figure 3: Monthly rainfall at Borroloola and Centre Island ...... 13 Figure 4: Wet season rainfall at Borroloola and Centre Island...... 13 Figure 5: Number of days each season where the maximum wind speed exceeded 20 knots at Borroloola and Centre Island...... 14 Figure 6: Minimum air temperatures at Borroloola from May-August in 2009-2012 ...... 15 Figure 7: Fisher trips at King Ash Bay based on state of residence ...... 16 Figure 8: Profile of daily trailer counts (and standard deviation) at the King Ash bay boat ramp ...... 17 Figure 9: Start and finish times for trips from King Ash Bay boat ramp...... 18 Figure 10: Destination for fishing trips by season...... 19 Figure 11: Locations of fishing trips showing intensity of fishing effort...... 19 Figure 12: Median length of fishing trips ...... 21 Figure 13: Percentage of days each season when trailer counts were made at the King Ash Bay boat ramp...... 23 Figure 14: One of the houseboats operating out of King Ash Bay ...... 24 Figure 15: Estimate of total number of trips each season from winter 2009 to autumn 2012...... 26 Figure 16: Adjusted catch rates per fishing trip each season ...... 28 Figure 17: Catch rates of Barramundi each season...... 29 Figure 18: Percentage of trips catching Barramundi each season ...... 29 Figure 19: Barramundi annual catch rates for fish caught and kept per trip ...... 30 Figure 20: Tagging grid maps covering the project area ...... 33 Figure 21: Tagging map showing the grid for locations where fish are tagged ...... 33

McArthur River Monitoring page 3 Figure 22: Barramundi being tagged and measured ...... 34 Figure 23: Recaptured fish KA7381 showing algal growth on the tag...... 34 Figure 24: Tag and recapture certificate introduced in 2012...... 35 Figure 25: Barramundi tagged each season...... 36 Figure 26: Grid locations where Barramundi have been tagged...... 36 Figure 27: Growth of Barramundi compared with days out ...... 38 Figure 28: Distance Barramundi moved compared with days out ...... 38 Figure 29: Tagging and recapture locations for fish that moved ...... 39 Figure 30: Movement of fish tagged in the Calvert River in 2007 ...... 40 Figure 31: Movement of fish tagged in the McArthur River as part of MRM environmental monitoring 40 Figure 32: Tagged Barramundi being measured prior to release ...... 41 Figure 33: Size range of all Barramundi measured from 2009-12...... 41 Figure 34: Tagged and untagged Barramundi showing all fish and legal fish released ...... 42 Figure 35 : Percentage of legal and juvenile Barramundi measured each year ...... 42 Figure 36: River flows in the McArthur River and lengths of Barramundi over time ...... 44 Figure 37: Lengths of Barramundi over time showing recruits for the last 4 years...... 44 Figure 38: Locating small juvenile Barramundi is an important part of understanding recruitment ....45 Figure 39: Site of NT electrofishing surveys on the McArthur River at Borroloola in 2010 and 2012 ...46 Figure 40: Size range of fish tagged during the 2010 electrofishing survey ...... 46 Figure 41: Size range of Barramundi tagged and recaptured during the 2012 survey ...... 47 Figure 42: Typical Golden Snapper tagged around Centre Island ...... 47 Figure 43: Locations where Golden Snapper have been tagged...... 48 Figure 44: Sizes of measured Golden Snapper...... 49 Figure 45 : Sizes of Golden Snapper measured and kept ...... 49 Figure 46: Comparison of recapture rates from 4 river systems...... 50 Figure 47: Exploitation rates for the Daly, McArthur and Fitzroy rivers...... 51 Figure 48: Comparison of Barramundi lengths for the McArthur, Fitzroy and Weipa Rivers for fish measured in 2011...... 51 Figure 49: McArthur fishing trip data form ...... 55 Figure 50: Typical monthly tidal cycle for Centre Island (Nov 2012) ...... 56

TABLES

Table 1: Summary of trips each fishing season...... 21 Table 2: Estimate of the number of fishing trips from houseboats in 2010 ...... 24 Table 3: Estimate of the total number of trips in each year (summer - spring) ...... 25 Table 4: Person/days for residents and visitors to King Ash Bay and estimated number of fishing trips from 2007-2012 ...... 26 Table 5: Summary of fish caught on trips each season ...... 28 Table 6: Indicative estimate of annual recreational catch (kept) of Barramundi for the McArthur River30 Table 7: Top 15 species recorded in catches (all seasons)...... 31 Table 8: Exploitation rates for Barramundi in the McArthur River based on tagging and recaptures ...37

McArthur River Monitoring page 4 ACKNOWLEDGEMENTS

This project was an initiative of the King Ash Bay Fishing Club and was funded by the McArthur River Mining Trust. The support of the King Ash Bay Fishing Club committee and Presidents Keith Hallett and Norm Cunningham is acknowledged. The support of personnel working with the McArthur River Mine Community Benefit Trust is also acknowledged. Thanks go to Maurice Motlop of the Trust at the time and Shauna Mounsey of URS Australia Pty Ltd for their work in getting the project underway. Thanks to Caryn Schoolmeester, Phil Anning, Daniel Suggit and Louise Beilby for their liaison on the project and review of milestone reports.

The support of the Liathawirriyarra Sea Rangers in tagging fish is also acknowledged. Funding for the inclusion of the sea rangers was provided by Caring for our Country through Territory Natural Resource Management.

The support of the King Ash Bay community in assisting with the project in doing trailer counts, distributing information and tagging kits, collecting fishing trip and tagging details and promoting the project is acknowledged. Thanks go to Jamie and Bec McGuiness and Tarmo and Jo Koivumaki at the KAB Service Station, Keith and Erin Hallett at the KAB Mini Mart, Terri Turner at the KAB Lodge and Raymie Hulm for counting trailers. Also thanks to those that assisted in collecting fishing trip details including Terri Turner, Jane Skewes, Grant Nielsen and Daniel Harding.

Thanks also go to Northern Territory Fisheries for their support throughout the project, especially to Thor Saunders and Quentin Allsop for their assistance with the electrofishing survey.

The support of the Amateur Fisherman's Association of the Northern Territory (AFANT), especially Chris Makepeace and Craig Ingram, is also acknowledged. Chris and other members of AFANT provided practical support in going to King Ash Bay and assisting with the tagging of Barramundi during the project.

There were around 175 fishers that assisted with tagging of fish. The support of these fishers ensured that the target for Barramundi tagged was exceeded. While it is not possible to acknowledge everyone there were 22 fishers that tagged over 50 fish each and these should be acknowledged. This includes Steve Watson, Bill Sawynok, Ross Miller, Dave Simula, Geoff and Raymie Hulm, Daniel Powell, Sean Brinkley, Dave and Trudie Waite, Wendi Parsons, Bevan and Naomi Gill, Tim Harding, Daniel Harding, Quentin Allsop, Darryl Jenkins, Michelle Knee, Wayne Jeffery, Peter Standing, Laurie Backhouse, Brian and Sue Kelliher and Trevor Geltch. Also thanks to all fishers that caught a tagged Barramundi and reported the details.

Thanks also to Colton Perna of North Australia Freshwater Fish Survey, Matt Bird and Allan Doddrell of McArthur River Mine and Dean Thorburn of Indo-Pacific Environmental Pty Ltd for providing data on tagged Barramundi from their projects. These allowed all tagging and recapture data for the area to be aggregated and provide a more complete tagging record.

McArthur River Monitoring page 5 SUMMARY

Recreational fishing is the most important recreational activity in the McArthur River area for local residents in Borroloola and King Ash Bay and visitors. In 2009 the King Ash Bay Fishing Club (KABFC) expressed concerns for Barramundi stocks in the river and that lead to this project being initiated and funded by the McArthur River Mine Community Benefits Trust. In 2011 the Lianthawirriyarra Sea Rangers at Borroloola joined the project to assist with tagging, funded by Caring for our Country through Territory Natural Resources Management.

Over the past 3 years (12 seasons from winter 2009 to spring 2012) the project has collected baseline data on fish stocks in the McArthur River, particular Barramundi and Golden Snapper (from spring 2011). The following is a summary of the findings of the project.

Status of stocks in the McArthur River

The status of the fishing effort and stocks can be summarised as:

 Overall fishing effort is high and increasing with significant fishing pressure in the area, especially in the McArthur River, Crooked Creek, Carrington Channel and Davies Channel  Barramundi stocks are in reasonable shape  A low recapture rate of tagged fish, low exploitation rate and high fishing effort suggests a good population of Barramundi  Barramundi recruitment has occurred each year with perhaps a boost in 2011  Medium term sustainability is questionable with increasing effort and catch rates  Golden Snapper stocks are uncertain due to limited information

Those conclusions are based on the following information collected through this project.

Fishing characteristics

 Recreational fishing occurs throughout the whole river system based on public access points and around offshore islands  Barramundi is the primary target species for recreational fishers with Golden Snapper, Black Jewfish, Mangrove Jack and Barred Javelin being secondary targets  Commercial fishing is restricted to the foreshores and islands of the Gulf of Carpentaria and is not allowed in the rivers  There is a closed season to commercial fishing from 1 Oct - 31 Jan  There is indigenous fishing throughout the area with concentrated effort around Borroloola  There are boat ramps at King Ash Bay, Black Rock, Mule Creek and Borroloola  Boats are launched from the bank at Batten Point and other locations where there is access to the river  There are 6 houseboats that operate out of King Ash Bay that cater for fishing  Boats are moored from King Ash Bay to Batten Point  Landbased fishing occurs from King Ash Bay to Batten Point, Borroloola and other locations where there is public access to the waterways  Fishing is primarily a dry season activity from Mar/Apr - Nov/Dec each year as access to the area is often cut/restricted during the wet season  Fishing is mostly a daytime activity due to the increased risk from crocodiles at night

McArthur River Monitoring page 6 What influences fishing?

 Rainfall and river flows limit fishing to the dry season with no or limited access to King Ash Bay until May in 2010, mid-Apr in 2011 and late Feb in 2012  Wind speeds of over 20 knots restrict fishing to sheltered areas around offshore islands and to the river system  Maximum wind speeds exceeding 20 knots occurred on 77 of 91 days (85%) in spring 2009, 70 of 92 days (76%) in autumn 2011 which restricted fishing, 26 of 92 days (28%) in autumn 2010 and 32 of 91 days (35%) in spring 2012  Tides play an important role in day to day decisions on whether to go fishing, what times to go fishing and where to go fishing with tides with a moderate run being favoured for Barramundi  Low water temperatures in winter affect Barramundi with activity being reduced when temperatures fall below 22oC with little activity at temperatures below 18oC  Water temperatures were 19-21oC in June 2010, 15-19oC in June 2011 and 16-22oC in July 2012

Who goes fishing?

 Visiting fishers at King Ash Bay accounted for 82.9% of fishing trips with local fishers from Borroloola and King Ash Bay accounting for 17.1% of trips  Fishers from Queensland undertook 40.0% of all trips while fishers from New South Wales accounted for 22.3%  Fishers from the Northern Territory accounted for 21.2% of trips  Fishers came from Darwin (1.2%), Alice Springs (1.5%), Tennant Creek (0.8%) and Mount Isa (2.2%)

When do they go fishing?

 Fishing is a primarily a day time activity with most trips commencing between 5- 8:00am and finishing from 2-6:00pm  Around 1.6% of trips were overnight trips, mainly to offshore islands

Where do they go fishing?

 Most fishing trips are to estuary locations with an average of 7.7% of trips to offshore islands  Most estuary trips are to the McArthur River downstream from King Ash Bay (31.4%), Crooked Creek (Johnson River) (10.5%) and Carrington Channel (9.7%)  These 3 locations account for 51.6% of the total effort  Landbased fishing is mostly limited to between King Ash Bay and Batten Point and around Borroloola

What is a typical fishing trip?

 A typical boat fishing trip involves 2 fishers fishing for 8 hours  A typical landbased trip was 1 fisher fishing for 2 hours

How many fishing trips?

 An estimate of fishing trips per season was made based on trailers counted at boat ramp, number of boats with houseboats and number of landbased fishers  It was estimated that there were 16,507 trips in 2010, 17,097 in 2011 and 18,835 in 2012  Based on an assessment of visitor numbers at King Ash Bay and number of trips each year there was an upward trend in the number of trips

McArthur River Monitoring page 7 What is the catch?

 Details of the catch and effort were obtained for 3,198 fishing trips with 11.9% of trips catching no fish at all  On those trips there were 23,461 fish caught of which 9,438 (40.2%) were kept  Overall catch rates for the 12 seasons fluctuated from around 4-16 fish/trip and the numbers kept were 2-5 fish/trip  On those trips there were 6,874 Barramundi caught and 1,964 (28.6%) kept  Catch rates for Barramundi over the 12 seasons fluctuated from around 1-5 fish/trip and the numbers kept were 0.2-1 fish/trip  Catch rates for Barramundi were highest in spring 2010, spring 2011 and spring 2012  In spring 2010 77.5% of trips caught Barramundi while in spring 2011 it was 79.1% and in spring 2012 is was 79.2%  In spring 2010 Barramundi comprised 51.2% of the catch, in spring 2011 they were 45.2% of the catch and in spring 2012 they were 43.1%  The most caught species as a proportion of the total catch were Barramundi (29.3%), Golden Snapper (9.8%) and Forktail Catfish (6.6%)  The most kept species were Mud Crab (78.8%), Grass Emperor (72.0%), Black Jewfish (71.5%) and Mangrove Jack (66.7%)  The least kept species were Forktail Catfish (2.4%) and Sharks (5.4%)  Of the Barramundi caught 27.3% were kept  The indicative estimate of the annual recreational catch was 41t in 2010, 53t in 2011 and 38t in 2012 however these figure should be treated with caution  The commercial catch for the area from the Robinson River to Bing Bong, including the islands, has averaged around 33 tonnes per year which is less than 5% of the Northern Territory catch

Fishing competitions

 The King Ash Bay Fishing Club holds a monthly fishing competition for the heaviest of each species weighed in  The main competition is generally held over Easter and attracts a large number of entrants but was postponed in 2011 to the May Day weekend with 212 entrants

Barramundi tagging

 There were 4,503 Barramundi tagged and 87 recaptures with a recapture rate of 1.9%  Locations where fish were tagged were based on a 2x2km grid with Barramundi tagged in 200 grids and most fish were tagged at the mouth of the McArthur River (270) and at the Carpentaria Highway crossing at Borroloola (216)  The exploitation rate based on tagged fish and recaptures kept was low ranging from 1.0-1.1% from 2010-12  Tagging data were also available from the North Australia Freshwater Fish project by James Cook University in the Calvert River and from McArthur River Mine Monitoring project

Barramundi growth

 There were 72 fish that had met the criteria for use in calculating growth  The average annual growth was 85+65mm  22 (30.6%) fish were slow growing with a growth rate of less than 40mm/year or half the average growth rate

Barramundi movement

 There were 91 fish where the distance moved could be calculated

McArthur River Monitoring page 8  41.8% of fish were recaptured in the same area as tagged  Of fish recaptured within 1 year the greatest distance moved was 50km  For fish recaptured after 1 year the greatest distance moved was 130km  All recaptures were from the McArthur River area however there were movements of fish between waterways, particularly for fish tagged in the lower reaches  2 of 33 Barramundi tagged in the Calvert River as part of the north Australia Freshwater Fish project were recaptured at the McArthur River mouth (moved 210km) and the Wearyan River mouth (moved 200km)  9 of 202 Barramundi tagged as part of the mine monitoring program were recaptured with 1 fish moving 100km and another 160km down river

Barramundi sizes

 There were 6,434 Barramundi measured of which 4,477 (69.6%) were tagged  Of the fish tagged 2,204 (49.2%) were over the legal size of 550mm  Of the 1,957 untagged fish measured 1,577 (80.6%) were over legal size  Of the untagged fish measured 1,702 (86.9%) were kept and 256 (13.1%) released  There were 49 Barramundi measured at 1.0m or longer with 30 kept (61.2%)  The largest Barramundi measured 1.3m and was kept  In 2009 66.8% of all fish measured were over legal size while in 2012 this as fallen to 55.5%

Barramundi recruitment

 Recruits are those fish below legal size  There were new recruits recorded in each year  There was insufficient information to assess relative recruitment from year to year however 2011 could have been a better year than the others

Electrofishing Surveys

 NT Fisheries undertook electrofishing surveys in the river at Borroloola in 2010 and 2012 to assist with assessing recruitment  In Nov 2010 there were 79 fish recorded while in Jul 2012 there were 51 fish recorded  Both surveys recorded recruits but the numbers were insufficient to assess relative recruitment

Golden Snapper tagging

 Tagging of Golden Snapper was added to the project in Oct 2011  A total of 203 fish were tagged with no recaptures  There were 38 grids where Golden Snapper were tagged with 42 fish tagged at Centre Island (KAB/U3) and 22 in Davies Channel (KAB/K3)  There were 944 fish measured with 689 (73.0%) 350:499mm in length  The largest fish measured and tagged was 755mm

Comparison with other river systems

 The recapture rate of 1.9% in the McArthur River compares with 7.1% in the Daly River, 0.8% in the Weipa rivers and 15.4% in the Fitzroy River  Exploitation rates in McArthur River ranged from 1.0-1.1% from 2010-12 while were 3- 1-4.1% for the Daly River (long term average 2.7%) and 1.3-2.9% for the Fitzroy River (long term average 4.6%)  In 2011 most Barramundi measured in the McArthur River were 500:549mm, in the Fitzroy River were 450:499mm and in the Weipa rivers were 400:449mm

McArthur River Monitoring page 9 1. BACKGROUND

Recreational fishing is a significant component of the tourist industry providing income to Darwin and to regional areas around the Northern Territory. King Ash Bay (KAB), on the McArthur River, in particular has become a popular recreational fishing location. As a result over the last few years it has received a large influx of tourists, who come to the area primarily for fishing.

During 2007, the King Ash Bay Fishing Club (KABFC) recorded around 40,000 visitor nights, with average stays of three nights per person (approximately 13,000 visitors in total). Of the approximately 13,000 people who visited KABFC in 2007, around 4,000 people came directly to KAB from their point of origin and the remaining 9,000 people passed through while travelling around Northern Australia1.

A concrete boat ramp at KAB provides access to a large system of rivers and channels, including the McArthur River, Carrington Channel, Batten Creek and Crooked Creek, which lead to the Gulf of Carpentaria approximately 30 kilometres downstream. Barramundi is the primary species for fishing within the river system, while offshore fishing commonly targets Mackerel, Tuna and reef fish around the Sir Edward Pellew Islands group.

The KABFC community propose to undertake an extensive baseline study to examine the impacts that increased recreational fishing is having on the Barramundi fishery in the McArthur River.

The project will involve collecting data that will allow recreational catch rates and catch to be estimated, fish movement and growth assessed and some information obtained on recruitment. Data will be collected through obtaining details of fishing on the McArthur River through fishing trip records and undertaking boat ramp surveys, tagging barramundi and catching juvenile barramundi in throw nets. The results will then be compiled into a report and made publicly available.

2. PROJECT OBJECTIVES

The objectives of this project from 2009-11 were:

1. To undertake a two year baseline survey to gather data relating to the status of the Barramundi fishery within the McArthur River.

2. Provide results of the baseline study to the King Ash Bay Community, McArthur River Trust Fund and the Northern Territory Government.

3. Establish an education centre to promote the project and encourage good fishing practices.

The project was extended to 2012 with the following objectives:

1. Obtaining an annual estimate of recreational catch and effort in the McArthur River, particularly Barramundi for 2012 (from summer 2011 to spring 2012).

2. Obtaining further data on annual Barramundi recruitment.

3. Obtaining data on growth and movement of Barramundi and Golden Snapper.

1 From King Ash Bay Fishing Club

McArthur River Monitoring page 10 3. PROJECT AREA

The project area is the McArthur River downstream from Borroloola, the McArthur River delta, coastal streams from Bing Bong to the Wearyan River and adjacent offshore islands as shown in figure 1.

WestIsland North Island Black Islet

Bing Bong

k e e r C

le Centre Island u M Vanderlin Island South WestIsland

k ee Cr la rri D a av K aw ie elly T s C Ch ha ann nn el el

l e n n a h C el n nn to ha g C in ie rr ur a C C Warren Inlet

Ba tte n C Dugong Creek re ek r ive r R Rutherford Creek thu Ar Mc Chadwick Creek

k King ree C Ash ten Jo at Bay hn B so n R iv er r e r iv e r R h thu tc Ar le c F M e h T

r e v i

r e n iv a R y r r u a h t e r A c W Borroloola M PROJECT AREA

Figure 1: McArthur River project area

4. FISHING CHARACTERISTICS

Recreational fishing is the most important recreational activity in the McArthur River area and has the following characteristics:

1. Fishing is primarily carried out from March/April to November/December each year depending on the wet season. 2. Wet season fishing is limited mostly to the residents of King Ash Bay and Borroloola and is further limited by rainfall and the flow conditions in the river. 3. Much of the fishing activity is undertaken by visitors to the area coming from all States. 4. There is a commercial netting closure that extends from near Bing Bong to Sharker Point2 as shown in figure 2 and a closed season to commercial netting for Barramundi from 1 October to 31 January.

2 Map obtained from http://fishingterritory.com/northern-territory-net-closure-line-maps/

McArthur River Monitoring page 11 Figure 2: Commercial netting closures adjacent to the McArthur River

Recreational fishing effort in the McArthur River has the following characteristics:

1. Barramundi is the primary target species with Golden Snapper, Black Jewfish, Mangrove Jack and Barred Javelin being secondary targets. 2. There are 3 modes of fishing being trailer boats, shore fishing and houseboat fishing. 3. There are 5 boat ramps in the area used by trailer boats being King Ash Bay (primary), Black Rock, Borroloola (2 ramps) and Mule Creek near Bing Bong. 4. Boats are launched from the bank at Batten Point. 5. Boats are moored from King Ash Bay through to Batten Point. 6. Shore based fishing is primarily carried out from King Ash Bay to Batten Point and at Borroloola. 7. There are 6 houseboats that operate in the river and these cater for up to 6 trailer boats. 8. Wind speed does not significantly influence fishing activity however strong winds can limit the areas fished to the rivers and affect catch rates. 9. Fishing is mainly a daylight activity from around daylight to dark. 10. Fishing is mainly within estuaries with a small proportion of trips to offshore islands. 11. There are a small proportion of overnight fishing trips, mostly to offshore locations, when the weather is suitable. 12. There is indigenous fishing that occurs throughout the area with some concentrated effort around Borroloola.

McArthur River Monitoring page 12 5. WHAT INFLUENCES FISHING?

The weather and tides plays a key role in determining fishing activity. The most important factors are rainfall, wind speed, tides and water temperature (particularly for Barramundi).

Rainfall

In the McArthur River area rainfall occurs mostly during the wet season from around Nov-Apr with little rain during the rest of the year. This reduces fishing effort during the wet season months to minimal or none at all, particularly during periods of flooding.

600 BORROLOOLA AND CENTRE ISLAND Cyclone Paul RAINFALL 500 Borroloola Centre Island 400 ) M M (

L 300 A F N I A R 200

100

0 9 9 9 9 9 9 9 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ------l l l l t t t t r r r r r r c c c n g p v n b y n g p v n b y n g p v n b y n g p v u c u c u c u c a p a p a p e e e u u e o a e a u u e o a e a u u e o a e a u u e o J J J J J O J J O J J O J J O F A F A F A M M M A S N D A S N D A S N D A S N M M M

Figure 3: Monthly rainfall at Borroloola and Centre Island

2000 WET SEASON RAINFALL 1800

Borroloola 1600 Centre Island 1400 )

M 1200 M (

L 1000 A F N I

A 800 R

600

400

200

0 2009-10 2010-11 2011-12

Figure 4: Wet season rainfall at Borroloola and Centre Island

Figure 3 shows monthly rainfall and figure 4 shows the wet season rainfall at Borroloola and Centre Island3. In the 2009-10 wet season Cyclone Paul affected the area in late Mar-Apr. Due to the cyclone and heavy rain the King Ash Bay Road was impassable until early May. This

3 Data on rainfall obtained from the Bureau of Meteorology website at www.bom.gov.au

McArthur River Monitoring page 13 resulted in the cancellation of the fishing competition that was to be held over Easter and delayed the arrival of visitors.

While there was no cyclone in the area in 2011 the overall rainfall was higher, especially in Feb and Mar at Centre Island. This resulted in the road being closed and visitors did not get to King Ash Bay until mid-Apr.

Wet season rainfall in 2011-12 was lower than in the previous 2 years with most of the rainfall in Dec. The King Ash Bay Road was only intermittently closed in early 2012 with some visiting fishers arriving in late Feb-Mar.

Wind Speed

While rainfall limits access to the area and affects fishing on a seasonal basis wind speed affects decisions about going fishing on a day to day basis. Strong winds can influence the decision to go fishing or at least influence the fishing location. Strong winds generally restrict offshore fishing and limit it to more sheltered river locations.

Wind speed is based on readings at Borroloola and Centre Island4. Generally wind speeds at Centre Island are greater than at Borroloola and significantly more variable. Wind speeds at 9:00am are typically less than 10 knots at Borroloola and 10-15 knots at Centre Island. Wind speeds generally reach their maximum during the middle of the day and then gradually abate from mid-afternoon. Wind speeds at 3:00pm are around 10 knots at Borroloola and 10-15 knots at Centre Island. Maximum winds speeds vary considerable. The number of days each season where the maximum wind speed exceeded 20 knots is shown in figure 5. This provides an approximate indicator of the affect of wind on fishing activities.

90 DAYS MAX WIND SPEED OVER 20 KNOTS Borroloola 80 Centre Island 70

S 50 Y A

D 40

0 - - - 9 0 1 2 9 0 0 1 1 2 2 9 0 1 0 1 1 1 0 1 1 1 1 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 r r r 2 2 2 2 2 2 2 2 2 2 2

e e e 0 1 2 r r r r g g g g n n n 1 1 1 e m e m e m e n n n n t i t i t i t i m m m r r r r n m n m n m n u u u i i i i p p p p t t t u u u S u S u S u S W S W S W S W A A A

Figure 5: Number of days each season where the maximum wind speed exceeded 20 knots at Borroloola and Centre Island Wind speed at Borroloola shows a seasonal pattern with more days in spring where the maximum wind speed exceeds 20 knots. In spring 2009 at Borroloola there were the most days when the maximum wind speed on 77 of 91 days (85%) exceeded 20 knots. Autumn 2011 recorded the most days at Centre Island where the maximum wind speed was over 20 knots on 70 of 92 days (76%). Autumn 2010 had the lowest number of days of maximum wind speed over 20 knots at Borroloola with 26 of 92 days (28%) while this was spring 2012 for Centre Island with 32 of 91 days (35%).

4 Wind speed obtained from the Bureau of Meteorology website at www.bom.gov.au

McArthur River Monitoring page 14 Most boat fishing trips can be characterised as boats leaving the boat ramp early in the morning when winds are light. In most seasons mean winds speeds at 9.00am were below 10 knots at Borroloola making travel to fishing destinations easier. Boats generally return to the boat ramp from mid-afternoon onwards when winds ease again. By 3:00pm in most months the mean wind speed had dropped back to around 10 knots.

Tides

Along with wind speed tides have the greatest influence on day to day decisions on whether to go fishing, what times to go fishing and where to go fishing. Fishers have different preferences for tides depending on whether they fish with bait or lures and what species they are targeting. Barramundi and other species can be caught at all stages of a tide however the locations fished will vary depending on the stage and speed of the tide. Large spring tides, eg 17 Nov 2012 as shown in Appendix 2, resulted in a strong runout flow of -2.19m and the low tide of 0.44m restricted access to many areas at low tide. Such tides are not favoured for Barramundi fishing. Conversely tides where there is little flow from low-high, eg +0.23m 26 Nov 2012, or high-low tide are also not favoured due to a lack of run. Tides where there is a moderate run are considered the best for Barramundi.

Water Temperature

Water temperature also influences fishing, particularly for Barramundi, however this is only an issue during late autumn and winter. Water temperatures were recorded during winter fishing trips by Infofish Australia staff. Minimum daily air temperature, as recorded by the Bureau of Meteorology5, at Borroloola provided an indicator of water temperature ranges over winter as shown in figure 6. Limited data were available for July-August 2012 (shown dotted in figure 6) due to no recordings being available for much of those months.

May WINTER AIR TEMPERATURES June July 20 August S I

U 15 C L E C

S E E

R 10 G E D

0 2009 2010 2011 2012 YEAR

Figure 6: Minimum air temperatures at Borroloola from May-August in 2009-2012

Barramundi activity steadily reduces when water temperature falls below 22oC and little activity occurs when the water temperature falls below 18oC. Water temperatures were not

5 Air temperature obtained from the Bureau of Meteorology website at www.bom.gov.au

McArthur River Monitoring page 15 recorded during 2009, while they generally ranged from 19-21oC in June 2010, from 15-19oC in June 2011 and 16-22oC in July 2012. Over the 4 years winter water temperatures were lowest in 2011. Low water temperatures generally result in lower catch rates for Barramundi during winter (see section 11).

6. WHO GOES FISHING?

Recreational fishing is the largest recreational activity in the McArthur River area with most of the fishing being undertaken by visiting fishers. Fishing trips are also undertaken by local residents of King Ash Bay and Borroloola. An assessment was made of the level of fishing by visiting and local fishers. Not all residents of Borroloola take part in fishing while most residents of King Ash Bay fish and visitors go fishing at least once during their stay.

Accurate information is not available on individual visitor numbers to King Ash Bay and visitor numbers are based on extrapolations of available data and informed assumptions. The following estimates were made for the local population and the number of visitors:

 Borroloola 2006 - 7736  King Ash Bay 2012 - 307  Visitors to King Ash Bay 2012- 3,500 - 5,5008 (not including cabins, lodge and houseboats)

When collecting details of fishing trips the home town or state for those taking part in the trip was recorded. Where members of the fishing party came from different places the home town was recorded for the boat owner or skipper. It was often the case for visiting fishers that members of the fishing party were from difference places however they were mostly from the same state.

WA, 0.9% ACT, 0.4%

SA, 3.2% TAS, 0.2% VIC, 11.7% QLD, 40.0% QLD NSW NT VIC SA WA ACT NT, 21.2% TAS

NSW, 22.3%

Figure 7: Fisher trips at King Ash Bay based on state of residence

There were a total of 2,979 trips where the home town was recorded. Figure 7 shows the number of trips undertaken by fishers from each state. A total of 82.9% of trips were undertaken by visitors to the area with fishers recorded from all States. The greatest number of fishers came from Queensland undertaking 40.0% of all trips while fishers from NSW undertook 22.3% of trips.

Fishers from the Northern Territory undertook 21.2% of all trips. The McArthur River is not recognised as a prime Barramundi location and that influences the numbers of the fishers that

6 From 2006 census and includes King Ash Bay 7 From King Ash Bay Fishing Club 8 Pers comm Norm Cunningham

McArthur River Monitoring page 16 are from the Northern Territory. Darwin fishers (1.2% of trips) have access to recognised Barramundi fishing locations that are much closer so not many fish at King Ash Bay.

Local fishers from King Ash Bay and Borroloola account for 17.1% of trips. This is higher than reported previously due to the inclusion of trips at Borroloola. Other Northern Territory fishers come from inland areas such as Alice Springs (1.5% of trips) and Tennant Creek (0.8% of trips). Fishing clubs from these areas have established bases at King Ash Bay and are regular fishers. King Ash Bay is also an important destination for fishers from Mount Isa (2.2% of trips) as it is within a day's drive of the city.

7. WHEN DO THEY GO FISHING?

Fishing is primarily a daytime activity as the risks associated with crocodiles increase significantly during the night. Trailers were counted at the King Ash Bay ramp at various times of the day to obtain a profile of use of the ramp throughout the day. The time that boats left the boat ramp and returned was also recorded for fishing trips so that a profile of start and finish times for fishing trips was able to be made.

Some visiting fishers, particularly those with small boats less than 4m, launch their boats from the ramp then moor them in front of their camp and return the trailer to their camp site. These trailers do not show up in the trailer counts at the boat ramp however start and finish times for these trips have been included where details of these trips were obtained.

A small proportion of trips involve overnight stays. These are generally trips to offshore islands where there is some accommodation and camping or they stay overnight on the boat. These trips can commence at any time of the day and leaving and returning times are often determined by offshore wind conditions. Details of overnight trips were obtained where possible.

35 KING ASH BAY BOAT RAMP USAGE 30 S

R 25 E L I A

R 20 T

F O

R 15 E B M

U 10 N

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1 1 1 1 1 1 1 1 1 2 TIME OF DAY

Figure 8: Profile of daily trailer counts (and standard deviation) at the King Ash bay boat ramp

Trailers were counted at various times of the day on 103 days at the King Ash Bay ramp where the number of trailers and the time were noted. This provided a profile of the numbers of trailers at the ramp at various times of the day.

McArthur River Monitoring page 17 These trailer counts indicated that boats leave to go fishing around dawn (4.30-6.30am) with most returning by, or just after, dark (4:30-6:30pm). The maximum numbers of trailers at the ramp are recorded from 9.00am-1:00pm as shown in figure 8.

For fishing trips the time of leaving the ramp or mooring and the time returning were recorded providing another measure of when fishing trips occur. Times from fishing trips indicate that most boats are out on the water by mid morning and start returning from midday to late afternoon as shown in figure 9. This corresponds to the numbers of trailers recorded at the ramp at various times of the day.

450 Trip starting and finishing times 400

350 Start time Finish time 300 s p i 250 r t

f o

o 200 N

150

100

0 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1 1 1 1 1 1 1 1 1 2 Time of day (hr)

Figure 9: Start and finish times for trips from King Ash Bay boat ramp

Fishing around offshore islands often involves an overnight stay, particularly when weather conditions are suitable. Trailers remaining overnight at the boat ramp have ranged from 0-10 however most times the number was 0-3. From 2,639 trips there were 43 trips (1.6%) recorded as being overnight so the overall proportion of overnight trips is low.

8. WHERE DO THEY GO FISHING?

When details of fishing trips were obtained a general fishing location was recorded. On many trips it was not uncommon for fishing to occur at a number of locations. For those trips the most distant or most fished location was recorded as the fishing location.

Assessments were made of destinations for trips to determine the proportion of trips to estuary and offshore locations. Based on the general fishing location a further analysis of fishing trips was made to determine fishing intensity throughout the area. The database was linked to Google Earth to allow visualisation of fishing intensity.

A total of 3,186 trips had a fishing location recorded. Most fishing trips were to estuary locations with less than 10% of trips in most seasons being to offshore locations as shown in figure 10. Trips to offshore locations are particularly influenced by wind speed (figure 5). The

McArthur River Monitoring page 18 distance to offshore fishing locations and the numerous safe overnight anchorages around the island are conducive to overnight trips. During suitable weather there are numbers of overnight trips, especially during autumn and spring.

estuaries Trip destinations offshore 100

s 60 p i r t

f 50 o

% 40

0 - - - n n n 9 0 1 2 9 0 1 2 9 0 1 0 0 1 1 1 2 1 0 1 1 1 m m m 0 1 1 0 1 0 1 0 1 0 0 0 0 0 u u u r r r 2 t 0 2 t 0 2 t 0 2 2 2 2 2 e e e 0 1 2 u 2 u 2 u 2 r r r r g g g g 1 1 1 m A m A m A e e e e n n n n t i t i t i t i r m r m r m r n n n n i i i i p u p u p u p S S S S S S S W W W W

Figure 10: Destination for fishing trips by season

Figure 11: Locations of fishing trips showing intensity of fishing effort

McArthur River Monitoring page 19 Figure 11 shows the intensity of fishing effort based on the primary location for fishing recorded for trips. The McArthur River downstream from King Ash Bay is the most fished location with 31.4% of all trips. Crooked Creek (Johnson River) is the second most fished location (10.5%) and Carrington Channel third (9.7%). These 3 locations account for around 51.6% of the total effort (shown in red). The McArthur River and Crooked Creek are the locations used by houseboats9 so the fishing effort there is even higher than indicated. Overall trips to offshore islands account for 7.7% of trips with Centre Island being the most fished area with 3.1% of trips.

The high number of trips to both the McArthur River and Crooked Creek are partly because both these are accessible at any stage of the tide. Many of the other locations have access restrictions around low tide and this deters many fishers, particularly those that are not familiar with the area.

There is some level of shore based fishing, primarily in the area from King Ash Bay to Batten Point and at Borroloola. At King Ash Bay this is mostly carried out by visitors without a boat. Most of these are southern visitors that go to the area with a caravan. The shore based fishing mainly occurs during the daytime in winter and early spring months. These fishers are generally less skilled than the boat fishers and catch rates are generally very low.

The landbased fishing at Borroloola is mainly around the Borroloola crossing and can be significant, particularly when there is a flow in the river.

9. WHAT IS A TYPICAL FISHING TRIP?

Fishing trips vary considerably. Boat trips vary in relation to the number of fishers in each boat and the duration of the fishing trip. To compare catch rates in different seasons a standard (typical) fishing trip was calculated. A typical fishing trip was defined as the median number of fishers fishing for a median number of hours.

Details of the number of fishers in each boat, time of leaving the boat ramp and returning were recorded as part of the fishing trip details. This provided the number of fishers and the length of the fishing trip. Fishing time was defined as the time from leaving the boat ramp and returning so includes travel time to, from and between fishing spots. In turn this allowed the trip to be converted to a typical fishing trip so that catch rates could be compared with other trips.

Landbased trips were separately identified as the characteristics of these trips are different to boat trips. Times for landbased trips are recorded as time fishing commenced to time fishing ceased so no travel time is included.

The median number of fishers per boat was 2 over all seasons. Table 1 provides a summary of typical fishing trips each season. Boat fishing trips were generally around 8 hours in duration with figure 12 showing the median length of trips per season. Trip length includes travel time and this can be significant as travel times of 2-3 hours per trip were not uncommon. Median trip length in spring 2012 was the highest at 9.6 hours and in autumn 2011 was the lowest at 6.0 hours. In general terms a typical boat fishing trip at King Ash Bay can be described as being 2 fishers fishing for 8 hours.

Most landbased trips were from around Borroloola with a total of 91 trips recorded. Landbased trips were typified as fishers fishing for a few hours before or after work. The median number of fishers for landbased trips was 1 fisher with a median fishing time of 2.0 hours.

9 Houseboat data will be incorporated into fishing effort once more data are obtained

McArthur River Monitoring page 20 Median Median Fishing Number Trip Number Effort of Length of hours Season trips hours fishers per trip winter 2009 28 6.4 2.0 12.8 spring 2009 315 8.0 2.0 16.0 summer 09-10 26 7.5 2.0 15.0 autumn 2010 486 8.3 2.0 16.6 winter 2010 279 7.0 2.0 14.0 spring 2010 222 9.5 2.0 19.0 summer 10-11 45 8.0 2.0 16.0 autumn 2011 505 6.0 2.0 12.0 winter 2011 194 8.0 2.0 16.0 spring 2011 249 8.75 2.0 17.5 summer 11-12 94 8.0 2.0 16.0 autumn 2012 196 8.5 2.0 17.0 winter 2012 300 7.5 2.0 15.0 spring 2012 259 9.6 2.0 19.2 Total 3198

Table 1: Summary of trips each fishing season

10 MEDIAN FISHING TRIP LENGTH 9

0 - - - 0 1 2 9 0 1 9 0 1 9 0 1 1 1 1 0 1 1 0 1 1 0 1 1 0 0 0 0 0 0 0 0 0 r r r 2 2 2 2 2 2 2 2 2

e e e 0 1 2 r n r n r n g g g 1 1 1 m m m e e e n n n t i m t i m t i m r m r m r m n u n u n u i i i p u t p u t p u t S S u S S u S S u W W W A A A

Figure 12: Median length of fishing trips

McArthur River Monitoring page 21 10. HOW MANY FISHING TRIPS?

Fishing trips are undertaken in a number of ways in the McArthur River area. These are:

 Boats launched from boat ramp or from the bank  Boats moored along the river  Boats tied up to houseboats  Landbased trips

Trailer Counts

Most fishing trips are undertaken from boats launched at boat ramps:

 King Ash Bay boat ramp  Moored boats adjacent to King Ash Bay boat ramp  Moored boats at King Ash Bay east  Black Rock boat ramp and moored boats  Launched or moored at Batten Point  Mule Creek boat ramp  Borroloola boat ramps

To estimate how many fishing trips are made trailer counts were made on as many days as possible. Each day that trailer counts were made the date, time of day and the number of trailers was recorded. As trailers come and go at the ramps during the day the total number of trips is greater than those counted at any hour. A correction factor was applied to estimate the total number of trips each day.

Calculating trips each season:

Total trips(day) = trailer count(hour) x 1/CF(hour) where Correction factor CF(hour) = boats fishing(hour)/total boats(day) and Boats fishing(hour) = boats(left ramp) - boats(returned ramp) Total trips(season) = average total trips(day) x days(season)

Getting trailer counts at the King Ash Bay ramp was the priority as 90% of the trailer boat fishing trips are from that boat ramp or from boats moored between King Ash Bay and Batten Point. Figure 13 shows the percentage of days when trailer counts were made at that ramp each season. There were 883 of 1,279 days (69%) when counts were made at the boat ramp. Seasons where trailer counts were low were spring 2010 and autumn 2012.

Each year the wet season determined when visitors were able to get to King Ash Bay and fishing commenced in earnest. During the wet season fishing trips were limited to local residents.

The wet season in 2009/10 lasted until April so fishing did not pick up until early May. During summer 2010/11 there were virtually no fishing trips in February due to the heavy rain and flooding. During autumn 2011 the road was cut until mid-Apr with very few vehicles able to get through so there was little fishing effort until mid-Apr with a rapid increase in trip numbers from that time. The wet season for 2011/12 had lower rainfall than in the previous 2 years and the road was open much earlier with fishing effort picking up rapidly from early March. This is the earliest that fishing commenced in the last 3 years.

Moored boat counts at Black Rock and Batten Point were mostly made during site visits however were included in local counts from winter 2011. A small number of trailer counts were made at the Mule Creek ramp at Bing Bong and at the boat ramps at Borroloola.

McArthur River Monitoring page 22 TRAILER COUNTS EACH SEASON 100%

80% E

G 60% A T N

E Non-count days C

R 40% Count days E P

20%

0% r r r n n n 9 0 0 1 1 2 2 9 0 1 2 e e e 0 1 0 1 1 1 1 1 2 1 0 1 1 1 m m m - - - 0 m 1 0 m 1 0 m 1 0 0 0 0 0 u u u 9 0 1 2 t 0 2 t 0 2 t 0 2 2 2 2 2 m m m 0 1 1

u 2 u 2 u 2 r r r r g u g u g u g 0 0 0 A A A e e e e n S n S n S n 2 2 2 t i t i t i t i r r r r n n n n i i i i p p p p S S S S W W W W

Figure 13: Percentage of days each season when trailer counts were made at the King Ash Bay boat ramp

Only the estimated numbers of trips from the KAB boat ramp are reliable as they are based on a sufficient number of days of trailer counts. The estimated number of trips from the boat ramp and moored boats were adjusted to obtain an estimate of the total trips per day.

The estimates for Mule Creek and Borroloola are considered to be indicative only as there were only a small number of days of observations however the usage of these was low compared to the KAB ramp.

Fishing from Houseboats

There are 6 houseboats that operate out of King Ash Bay. Houseboats are generally available from Apr/May through to the end of November. The houseboats are removed from the water around the end of Nov and are not returned to the water until the end of the wet season around mid-late Apr. Figure 14 shows one of the houseboats that operate out of King Ash Bay.

Fishing effort associated with these houseboats mainly occurs in Apr-May after the wet season and from Aug-Oct. There is little houseboat fishing during winter due to the low water temperatures which significantly reduces Barramundi catches and limits the attractiveness of hiring a houseboat. The houseboats can take from 4-12 people and have from 2-6 boats that use a houseboat as their base. Data on houseboat usage were obtained for the 2010 season for 4 of the houseboats. Data for 2011 and 2012 was not available at the time of completion of this report.

Houseboat usage is limited to the McArthur River and Crooked Creek. They are taken down the river and moored in the area intended to be fished. With each houseboat there were a number of smaller boats attached. The houseboat was used as a base with fishing being carried out from the smaller boats.

An estimate of the number of fishing trips from houseboats was made for 2010. The median of fishers per trip is 2 and this was used to estimate the number of trips. Two nights were subtracted from each trip to account for the houseboat travelling to and from the fishing destination.

McArthur River Monitoring page 23 The estimate of houseboat trips for each season was calculated as:

Houseboat trips(season) = (number of persons*(number of nights - 2))/2

Data were obtained for 4 of the 6 houseboats for 2010 with the boats operating from Apr/May to Sep/Oct. Data obtained were:

 Name of houseboat  Season of operation  Number of persons on boat  Number of nights for each trip  Location where the houseboat was stationed

Figure 14: One of the houseboats operating out of King Ash Bay

In 2010 for the 4 houseboats where data were available it was estimated that there were 3,466 trips. These were analysed on a seasonal basis to get a seasonal estimate of houseboat usage. Table 2 shows the breakdown of the estimate of houseboat trips each season. This was used to calculate the estimated total number of fishing trips from all houseboats.

Season Houseboats Estimated trips autumn 2010 4 1960 winter 2010 4 0 spring 2010 4 1506 summer 2010-11 0 0 Total 3466

Table 2: Estimate of the number of fishing trips from houseboats in 2010

McArthur River Monitoring page 24 Landbased trips

Landbased fishing occurs in a number of locations:

 Along the river bank from King Ash Bay to Batten Point  Along the river bank at Borroloola, particularly the river crossing on the Carpentaria Highway  At a number of locations where there are tracks leading to the river

It is difficult to estimate the number of shore based trips from King Ash Bay to Batten Point as many fishers cast out, prop up their rod(s) and then return to their camp, only attending the rod to rebait or if a fish is hooked. The number of "trips" is very low compared with boats trips and is likely to be in the range of 0-10 per day during the dry season.

At Borroloola the landbased trips are more conventional with fishing mainly for Barramundi using baits or lures. Most of these trips are in the vicinity of the river crossing on the Carpentaria Highway.

Estimates of landbased trips were made with 0-5 trips/day estimated depending on the season, however this should be treated with caution as there was no reliable data collection that supported these estimates and they were based on anecdotal information provided by fishers.

Estimating Fishing Trips

The total number of fishing trips each season was calculated as:

Total fishing trips(season) = ((Trailer counts(King Ash Bay) + moored boats(King Ash Bay - Batten Point) + Trailer counts(Mule Creek) + Trailer Counts(Borroloola) + Landbased trips)*CF + Houseboat trips))*number of days(season)

Assumptions that were used in arriving at the estimate were that 50% of the moored boats went fishing each day and 100% of houseboat boats went fishing each day.

Based on a year being from summer in one year to spring in the following year table 3 provides an estimate of the number of trips each year and each day. There was a slight increase in the number of trips from 2010-12.

Year Trips Trips/day 200910 9,261 51 2010 16,507 45 2011 17,097 47 2012 18,835 52

Table 3: Estimate of the total number of trips in each year (summer - spring)

Figure 15 shows the estimated number of trips each season. Houseboat trips were based on 2010 data and data for other years is shown dashed. Given the level of uncertainty in the houseboat data the error margin for the number of trips is likely to be in the order of 10-20%.

The Northern Territory fisher survey in 2009-10 estimated that there were 3,799 days fished by NT residents and 33,017 by visitors in the McArthur River area.11 While this cannot be

10 Data from 2009 is for winter and spring only and daily trips are an overestimate due to low number of trips in summer not being included

McArthur River Monitoring page 25 directly compared to the estimated number of fishing trips based on an average 2.1 persons/trips this equates to around 72 trips/day This estimate is higher than the estimate from this survey.

Houseboats 8000 season trips FISHING TRIPS PER SEASON 7000

6000 S

P 5000 I R T

G 4000 N I H S

I 3000 F

2000

1000

0 r r r 9 9 0 0 0 0 1 1 1 1 2 2 2 2 e e e 0 0 1 1 1 1 1 1 1 1 1 1 1 1 - - - 0 0 0 0 0 0 0 0 0 0 0 m m m 9 0 1 2 2 2 2 2 2 2 2 2 2 2

0 1 1 m m m r r r r g n g n g n g 0 0 0 u u u e e e e n n n n s 2 s 2 s 2 t t t t i i i i m m m r r r r n n n n u u u i i i i p p p p t t t w s w s w s w s u u u a a a SEASON

Figure 15: Estimate of total number of trips each season from winter 2009 to autumn 2012

Trends in Fishing Trips

Visitor numbers to King Ash Bay were obtained from the club to determine trends as an indicator of changes in fishing effort. Numbers are estimated based on the club's resident and camper revenue data and do not include visitors that stayed in the cabins, at the lodge or on houseboats. Therefore the figures are an underestimate of actual person days but indicate an upward trend. The years are based on a club financial year from Apr - Mar so are not the same as used for estimating fishing trips.

Year Person/days Change Fishing Trips Change 2007 40,000 2010 60,000 16,507 2011 58,600 -2% 17,097 +3% 2012 62,000 +8% 18,835 +10%

Table 4: Person/days for residents and visitors to King Ash Bay and estimated number of fishing trips from 2007-2012

Table 4 shows the estimated number of person/days and number of persons for 2007 and the last 3 years. It was also estimated that these figures had an error margin of 10-15%.12 Visitor numbers and the number of fishing trips for the past 3 years show an upward trend.

11 Survey of Recreational Fishing in the Northern Territory 2009-10, LD West, JM Lyle, SR Matthews, KE Stark and AS Steffe 2012 12 Pers comms Norm Cunningham based on King Ash Bay office records

McArthur River Monitoring page 26 11. WHAT IS THE CATCH?

Catch data were collected from details of fishing trips, either through boat ramp surveys or from fishers volunteering their fishing trip details. Catch was determined as the number of fish caught and the number of fish kept per trip. Catch rates were calculated for each trip and were adjusted to a typical fishing trip to allow catch rates to be compared from season to season. A typical boat fishing trip was 2 fishers fishing for 8 hours.

Effort and catch data were collected by obtaining details of fishing trips, either through boat ramp surveys or from fishers volunteering their fishing trip details. A standard form was used to collect details of a trip as shown in Appendix 1. Data collected includes:

 Date of trip  Number of fishers  Boat ramp used  Home town  Time left the boat ramp  Time returned to boat ramp  Location fished  Species caught and numbers kept and released  Length of fish if measured

Data for winter 2009 (28 trips) needs to be treated with caution due to the low number of trips for that season at the start of the project. There were few trips over summer in each year so that summer catch rates are not comparable with other seasons. Total fishing trips over summers were low due to the wet season, cyclones and flooding with local residents undertaking these trips.

From winter 2009 - spring 2012 (12 seasons) details of catch and effort were obtained from 3,198 trips. Table 5 provides a summary of the fish caught and released on trips each season. Of the 3,198 trips 382 (11.9%) reported no fish caught. Of total trips 1,855 (58.0%) reported catching at least 1 Barramundi.

Of the 23,461 fish caught on the trips 9,438 (40.2%) were kept. Catch rates for fish caught and kept each season are shown in figure 16. Overall catch rates fluctuated over the 12 seasons from around 4-16 fish/trip. The number of kept fish fluctuated from around 2-5 fish/trip.

Of the 6,874 Barramundi that were caught 1,964 (28.6%) were kept. Barramundi catch rates are shown in figure 17. High catch rates were recorded in spring 2010, spring 2011 and spring 2012 (excluding summers). Overall catch rates fluctuated over the 12 seasons from around 1-5 fish/trip. The number of kept fish fluctuated from around 0.2-1 fish/trip. While the kept fish rate per trip for Barramundi was low many fishers keep Barramundi over several trips until they reached the possession limit of 5 fish per person.

There were 2 trips recorded that exceeded the possession limit where 2 fishers kept 12 and 11 Barramundi, 2 trips where 2 fishers kept the possession limit of 10 and 23 trips (0.8% of all trips) where 2 fishers kept 5-9 Barramundi. The most Barramundi caught on a trip was 48 with all fish tagged and released.

In spring 2012 a party of 15 fishers from Queensland fished for around 10 days and kept Barramundi until the possession limit was reached for each fisher. The party kept 75 Barramundi in total and this was the largest combined catch recorded. The party was also not willing to provide details of their catch per trip. While this is not typical there were a number of fishing parties that fished with a similar objective, especially during spring when catch rates were highest. Houseboat fishers in particular had the objective of catching their possession limit.

McArthur River Monitoring page 27 Number No Trips Total Total of catch Barra Fish Fish Barra Barra Season trips trips caught caught kept caught kept winter 2009 28 6 6 106 62 9 6 spring 2009 315 66 165 1728 730 462 155 summer 09-10 26 5 18 126 69 63 26 autumn 2010 486 102 203 2730 1676 477 208 winter 2010 279 42 145 1548 631 486 113 spring 2010 222 8 172 2007 498 1027 196 summer 10-11 45 0 40 461 184 176 49 autumn 2011 505 80 258 3121 2163 556 365 winter 2011 194 19 112 1361 604 206 78 spring 2011 249 11 197 2332 578 1055 181 summer 11-12 94 0 57 1130 227 202 23 autumn 2012 196 4 128 2461 687 468 195 winter 2012 300 24 149 1930 753 463 121 spring 2012 259 15 205 2420 576 1224 248 Total 3198 382 1855 23461 9438 6874 1964

Table 5: Summary of fish caught on trips each season

22 CATCH PER TRIP 20 caught 18 kept 16 p

i barramundi caught per trip r t / 14 barramundi kept per trip h s i f

12 j d a 10 e g a

r 8 e v a 6

0 r r r 0 1 2 9 0 1 1 2 2 9 0 1 2 e e e 0 1 1 1 0 1 1 1 1 1 0 1 1 1 / / m 1 0 0 0 0 0 m 0 m 0 0 0 0 0 / 0 1 2 2 2 2 2 2 2 2 2 2 2 m 9 m m 1 1

r u n r n r n r g 0 g u g u g 0 0 e e e e S n n S n S n 2 2 t i m t i m t i m t i r r r r n u n u n u n i i i i p t p t p t p S u S u S u S W W W W A A A

Figure 16: Adjusted catch rates per fishing trip each season

McArthur River Monitoring page 28 6 BARRAMUNDI CAUGHT PER TRIP

5 barramundi caught per trip barramundi kept per trip

4 p i r t

/ 3 h s i f

0 - - - 0 1 2 9 0 1 2 9 0 1 2 9 0 1 1 1 1 0 1 1 1 0 1 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2

2 2 2

r n r n r n r g g g g r r r 0 1 2 e e e e n e n e n e n 1 1 1 t i m t i m t i m t i r r r r n u n u n u n m m m i i i i p t p t p t p S m u S m u S m u S W W W W u A u A u A S S S

Figure 17: Catch rates of Barramundi each season

100% TRIPS EACH SEASON CATCHING BARRAMUNDI 90%

80%

70%

60%

50%

40%

30%

20%

10%

0% - - - 0 1 2 9 0 1 2 9 0 1 2 9 0 1 1 1 1 0 1 1 1 0 1 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 r r r 2 2 2 2 2 2 2 2 2 2 2

e 0 e 1 e 2

r r r r n n n g 1 g 1 g 1 g m m m e e e e n n n n t t t t i m i m i m i r m r m r m r n n n n u u u i i i i p u t p u t p u t p s s s s s s s w w w w u u u a a a

Figure 18: Percentage of trips catching Barramundi each season

Figure 18 shows the percentage of trips each season where Barramundi were caught. In spring 2010 there were 172 (77.5%) trips, in spring 2011 there were 197 (79.1%) trips and in spring 2012 there were 205 (79.2%) trips that caught Barramundi.

In spring 2010 Barramundi were 51.2% of the catch and were 39.3% of the kept catch, in spring 2011 they were 45.2% of the catch and 31.3% of the kept catch and in spring 2012 they were 50.6% of the catch and 43.1% of the kept catch.

McArthur River Monitoring page 29 3 BARRAMUNDI ANNUAL CATCH RATES

barramundi caught per trip 2.5 barramundi kept per trip

2 P I R T

/ 1.5 H S I F

0.5

0 2009 2010 2011 2012

Figure 19: Barramundi annual catch rates for fish caught and kept per trip

Figure 19 shows the annual catch rates for Barramundi caught and kept. Over the 4 years there has been an increase in the catch rate of fish per trip while the catch rate for fish kept rose from 2009-11 and declined in 2012. There was a drop in the proportion of legal sized fish in the catch in 2012 (see section 14).

Given the uncertainty in the houseboat data and the number of trips each year any estimate of the catch of Barramundi should be treated with caution and is only provided as an indicative estimate. The annual catch of Barramundi can be calculated as:

Catch(tonnes) = Number of trips(year) x annual kept catch rate(trip) x average weight(kept fish)

Av Kept length Weight catch Catch year trips (mm) (kg)13 rate (t) 2009 9,261 2010 16,507 697 3.8 0.65 41 2011 17,097 715 4.1 0.75 53 2012 18,835 675 3.7 0.55 38

Table 6: Indicative estimate of annual recreational catch (kept) of Barramundi for the McArthur River

Table 6 shows the indicative annual estimate of the annual catch of Barramundi. This compares with the annual commercial catch of around 33t for the area from the Robinson River to Bing Bong, including the islands. This is 5% of the total commercial catch in the Northern Territory. While the figures need to be treated with caution it is likely that the recreational catch exceeds the commercial catch, especially as the Wearyan River is not included in the estimate.

Table 7 shows the top 15 species caught on all trips over all seasons. Barramundi is the most caught species. Golden Snapper is the second most caught species and Forktail Catfish third.

13 Average weight for fish of average length obtained from Suntag database

McArthur River Monitoring page 30 Blue Threadfin, Queenfish, Goldspotted Rockcod and Barred Javelin are the next most caught species.

The most kept species were Mud Crab (78.8%), Grass Emperor (72.0%), Black Jewfish (71.5%) and Mangrove Jack (66.7%). Least kept were Forktail Catfish (2.4%) and Shark (not specified) (5.4%). Of the Barramundi caught 27.3% were kept.

SPECIES Caught Kept % Kept BARRAMUNDI 6866 1874 27.3% GOLDEN SNAPPER 2289 1323 57.8% FORKTAIL CATFISH 1545 37 2.4% BLUE THREADFIN 1344 818 60.9% QUEENFISH 1342 535 39.9% GOLDSPOTTED ROCKCOD 1299 269 20.7% BARRED JAVELIN 1068 560 52.4% MUD CRAB 1048 826 78.8% BLACKSPOTTED ROCKCOD 1009 380 37.7% PIKEY BREAM 915 532 58.1% SHARK 614 33 5.4% MANGROVE JACK 610 413 67.7% GRASS EMPEROR 483 348 72.0% BLACK JEWFISH 386 276 71.5% TREVALLY 269 120 44.6%

Table 7: Top 15 species recorded in catches (all seasons)

12. FISHING COMPETITIONS

The King Ash Bay Fishing Club has a number of fishing competitions throughout the year. There is a monthly competition for the heaviest fish of each species weighed in. There is also an annual fishing competition held over Easter which attracts many entries. In 2010 the fishing competition was delayed due to Cyclone Paul and it was held on the Anzac Day weekend (24- 25 April) instead.

In 2011 there were 2 competitions. One was held on Easter Sunday (24 Apr) and another on the May Day weekend (30 Apr-2 May).

The Easter competition had 50 entries and there were 5 Barramundi weighed in. The May competition had 212 entries with 15 Barramundi weighed in. Surveys were undertaken during both competitions and details of 124 fishing trips were obtained. These have been included in the seasonal analysis. Lengths were obtained from all Barramundi weighed in at both competitions.

In 2012 the main competition was held over Easter (7-8 Apr). Results of that competition are not yet available. A new monthly Mystery Team Fishing Competition was introduced in Jul 2012 with 5 Barramundi weighed in, 2 Black Jewfish, 6 Pikey Bream and 2 Mangrove Jack. For this competition the maximum length of Barramundi that could be weighed in was 1m. This competition will alternate with an individual competition each other fortnight.

McArthur River Monitoring page 31 13. BARRAMUNDI TAGGING

Tagging kits (including tagging instructions) were made up and provided to local and visiting volunteer fishers to assist with the tagging.

Tagging kits contained the following:

 Tagging applicator and tags  Waterproof tagging record book to record tag details and pencil  Measuring ruler  Grid maps  Information folder with forms to lodge fishing trip and tagging details

Many taggers provided details of all fish caught on a trip allowing the data to be used for catch and effort while others only provided the details of fish tagged. However not all tag records were submitted as some were lost, misplaced or failed to be handed in. Tagging data were stored in the Infofish Australia Suntag database.

Tagging was carried out by:

 Infofish Australia  Members of King Ash Bay Fishing Club  Fishers at Borroloola  Visiting volunteer fishers  NT Fisheries during electrofishing surveys

A series of grid maps were produced covering the project area to allow easy identification of locations where fish were tagged. Figure 20 shows the maps covering the project area while figure 21 shows one of the individual maps with the grid. With Barramundi being tagged above the Borroloola Crossing a further map was added in early 2012 to cover additional tag locations. Locations are recorded using the map and grid code eg KAB (map) Q7 (grid) which is the mouth of the McArthur River.

Figure 22 shows a typical Barramundi being tagged. The club offered a reward of $25 for the reporting of recapture details. Figure 23 shows one of the recaptures, KA7381 with extensive algal growth on the tag. Recaptures were reported through:

 King Ash Bay Service Station  1800 toll free phone number  King Ash Bay Monitoring and Suntag websites  email or direct to Infofish Australia

A certificate for each recapture was provided to both the person that recaptured the fish and the person that tagged the fish. A certificate specific to the project was introduced in early 2012 as shown in figure 24. Feedback was also provided by email if an email address was available and most recaptures were placed on the project's Facebook page from early 2012.

Not all recaptures were reported. Feedback indicated that some recreational fishers did not report recaptures. There was evidence that a number of recaptures were made by commercial fishers however none of these were reported. A number of recaptures by indigenous fishers, particularly at Borroloola, were made but not reported.

McArthur River Monitoring page 32 Figure 20: Tagging grid maps covering the project area

Figure 21: Tagging map showing the grid for locations where fish are tagged

McArthur River Monitoring page 33 Figure 22: Barramundi being tagged and measured

Figure 23: Recaptured fish KA7381 showing algal growth on the tag

McArthur River Monitoring page 34 Figure 24: Tag and recapture certificate introduced in 2012

Figure 25 shows the number of Barramundi tagged each season with 4,503 fish tagged to spring 2012 and 87 (1.9%) recaptures.Tagging details are available for all except 1 recapture. There have been 37 fish (43.0%) recaptured over a year after being tagged. The longest time between tagging and recapture was 875 days (2.4 years).

The recapture rate is the ratio of recaptures to fish tagged and provides an indicative measure of fishing pressure on fish stocks. The higher the recapture rate the greater the fishing pressure. By comparison in Queensland in the Fitzroy River the recapture rate for Barramundi is 19.3%14.

Figure 26 shows the locations where fish have been tagged. There were 4,322 Barramundi tagged with the map/grid recorded. There were 200 map grids where Barramundi have been tagged. The greatest numbers of Barramundi were tagged in grid Q6 on map KAB (McArthur River mouth) with 270 and grid S15 on map BOR (Borroloola Crossing) with 216. There were 7 grid locations where 100 or more fish were tagged and 13 grid locations where 50-99 fish were tagged.

Google Earth has become a tool that is commonly used by recreational fishers. While figure 25 is a static image anyone with Google Earth can view this and other data interactively. The database has been linked to Google Earth to provide new ways of presenting the data to researchers, managers and the community in a more understandable format.

14 Suntag Research Report 2009/10

McArthur River Monitoring page 35 900

BARRAMUNDI TAGGED 800

Non trip 700 trip

600 D E

G 500 G A T

H 400 S I F 300

200

100

0 0 0 1 1 2 2 9 0 1 2 9 0 1 2 1 1 1 1 1 1 0 1 1 1 0 1 1 1 - - - 0 0 0 0 0 0 0 0 0 0 0 9 0 1 2 2 2 2 2 2 2 2 2 2 2

0 1 1

r r r r n n n g 0 g 0 g 0 g e e e e n 2 n 2 n 2 n t t t t i m i m i m i

r r r r r r r n n n n u u u i i i i p e t p e t p e t p s s s s w w w w u u u m m m a a a m m m u u u s s s

Figure 25: Barramundi tagged each season

Figure 26: Grid locations where Barramundi have been tagged

McArthur River Monitoring page 36 The exploitation rate is the ratio of recaptures where the fish was kept compared with the number of fish tagged over time. This provides an estimate of the proportion of population harvested. The exploitation rate was calculated as:

Exploitation rate = recaptures kept(tag year) + recaptures kept(tag year-1)/ fish tagged(tag year-1) * 90% survival rate

Recaptures Recaptures Recaptured Recaptured from previous from current from tags Exploit Tag 90% from current years tagging and previous released > 1 Total ation year Tagged survival years tagging year year year ago recaps rate Recap Kept Recap Kept Recap Kept Recap Kept 2009 216 194.4 0 0 2010 1415 1273.5 7 4 3 2 3 2 0 0 10 1.0% 2011 1410 1269 6 4 24 10 31 14 5 3 35 1.1% 2012 1436 1292.4 10 3 17 10 23 14 15 11 42 1.1% 87

Table 8: Exploitation rates for Barramundi in the McArthur River based on tagging and recaptures

Table 8 shows the exploitation rates for each year based on the number of fish tagged and the number of recaptures kept. The exploitation rate ranged from 1.0-1.1% each year which is a low rate. Comparison of exploitation rates with the other rivers is in section 18.

14. BARRAMUNDI GROWTH

Tag and recapture data were used to calculate growth. Growth rates were calculated as:

Annual growth rate (mm/year) = (TLR - TLT)/days out*365 where

TLR = total length when recaptured TLT = total length when tagged days out = number of days between tagging and recapture

A total of 96 recaptures (including 9 fish from the MRM Environmental Monitoring tagging) have now been recorded. An analysis of growth was made for fish that were at liberty for a minimum of 90 days. Fish that had negative growth were excluded. There were 72 fish (including 8 fish from the MRM Environmental Monitoring tagging) that met these criteria.

The average annual growth rate was 85+65mm which indicates that the growth rate is very variable. Figure 27 shows the growth of fish compared to the days out with the trendline indicating the growth rate over time. The data suggests that some fish grow very slowly, 22 (30.6%) grew less than 40mm/year or half the average, while there are others that grew faster that average.

McArthur River Monitoring page 37 300 GROWTH RATE OF BARRAMUNDI 250 )

M 200 M (

T 150 W O R 100 G

0 0 100 200 300 400 500 600 700 800 DAYS OUT

Figure 27: Growth of Barramundi compared with days out

15. BARRAMUNDI MOVEMENT

Tag and recapture data were used to determine movement based on the grids recorded when the fish was tagged and recaptured. The distance fish moved was calculated using MapInfo GIS or Google Earth software and was calculated as the shortest water distance between the locations where the fish was tagged and recaptured.

140

DISTANCE BARRAMUNDI MOVED 120

) 100 M K (

E 80 V O M

C 60 N A T S I

D 40

0 0 100 200 300 400 500 600 700 800 900 1000 DAYS OUT

Figure 28: Distance Barramundi moved compared with days out There were 91 recaptures (including 8 fish from the MRM Environmental Monitoring tagging) where the distance between tagging and recapture was able to be calculated.

McArthur River Monitoring page 38 Figure 28 shows the movement of fish tagged compared with the days out. There were 38 (41.8%) fish were recaptured in the same area as they were tagged. Of the fish recaptured within one year the greatest distance moved was 50km. Fish recaptured after being at liberty for more than a year showed greater movement with one fish having moved 130km.

KA0286 TAGGED KA1801 RECAPTURED

KA4763/KA0173 KA0286 TAGGED RECAPTURED

KA1801 TAGGED KA3262 KING RECAPTURED KA4103 k ASH ree n C RECAPTURED tte BAY Ba KA0121 KA4763 TAGGED RECAPTURED KA3262 KA0121/KA3108 KA3108 TAGGED RECAPTURED TAGGED

KA0173 RECAPTURED

r e TAG LOCATION iv R

r RECAPTURE LOCATION u h t r A c Borroloola M

KA4103 TAGGED

Figure 29: Tagging and recapture locations for fish that moved

Figure 29 shows the movement of some of the fish recaptured. This indicates that fish move between different parts of the McArthur River delta system.

As well as the Barramundi tagged as part of this project, there are 2 other projects that have tagged Barramundi adjacent to the project area. These are:

 North Australia Freshwater Fish project (James Cook University)  McArthur River Mine Monitoring project (Indo-Pacific International Pty Ltd)

Access has been provided to these data and aggregated data from the 3 projects will present as complete a picture as possible of tagging relevant to this project. Additional data from the Mine Monitoring program for 2012 will be reviewed when available.

There have been 4 (12.1%) recaptures from tagging of 33 Barramundi as part of the North Australia Freshwater Fish project in 2007. These fish were tagged in the Calvert River. Two of the recaptures were in the Calvert River while 2 were recaptured in the project area (figure 30). This indicates that there is some westward movement of Barramundi in the area.

There have been 9 (2.5%) recaptures of 202 fish tagged as part of the McArthur River Mine environmental monitoring project. One was recaptured at the mouth of the McArthur River in August 2010 having moved 130km down river and 2 were recaptured by NT Fisheries during their electrofishing survey at Borroloola crossing (figure 31). Another fish tagged above Borroloola was recaptured 13km down river below the Borroloola crossing in Oct 2011.

McArthur River Monitoring page 39 R48198 recaptured

Borroloola er Riv ur rth R48257 recaptured cA r M e v i R

n a y r a e

r e iv R rt e lv a C

R48198 tagged

R48257 tagged

Figure 30: Movement of fish tagged in the Calvert River in 2007

MR00472 RECAPTURED

KING ASH BAY

BOROOLOOLA MR00371 RECAPTURED

MR00371 MR00472 TAGGED

Figure 31: Movement of fish tagged in the McArthur River as part of MRM environmental monitoring

McArthur River Monitoring page 40 16. BARRAMUNDI SIZES

The lengths of Barramundi were recorded for tagged fish and fish were also measured by fishers and provided on their trip forms. Figure 32 shows a typical tagged Barramundi being measured on a brag mat.

Figure 32: Tagged Barramundi being measured prior to release

400 BARRAMUNDI LENGTHS BY YEAR 350 2009 300 2010 H

S 2011 I 250 F

2012 F O 200 R E B

M 150 U N 100

0 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 1 1 2 2 3

1 1 1 1 1 1 1 : : : : : : : : : : : : : : : : : : : : : : : : : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 1 1 2 2 3 1 1 1 1 1 1 1 SIZE RANGE (MM)

Figure 33: Size range of all Barramundi measured from 2009-12

McArthur River Monitoring page 41 There were a total of 6,434 Barramundi measured. Figure 33 shows the size range of Barramundi measured each year. Of those 4,477 (70.0%) were tagged with 2,204 (49.2%) over the legal size of 550mm. Of the 1,957 untagged Barramundi measured 1,577 (80.6%) were over legal size.

5000 RELEASED BARRAMUNDI 4500

4000 ALL LEGAL 3500 H S I 3000 F

F O 2500 R E B

M 2000 U N 1500

1000

500

0 TAGGED UNTAGGED

Figure 34: Tagged and untagged Barramundi showing all fish and legal fish released

JUVENILE LEGAL AND JUVENILE BARRAMUNDI MEASURED LEGAL 100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

0% 2009 2010 2011 2012 YEAR

Figure 35 : Percentage of legal and juvenile Barramundi measured each year

McArthur River Monitoring page 42 Of 1,957 untagged measured fish over legal size there were 1,702 (86.9%) kept and 256 (13.1%) that were released. Figure 33 shows the number of released tagged and untagged Barramundi and the number of legal fish released.

There were 49 fish measured at 1,000mm (1.0m) of which 30 (61.2%) were kept with the longest fish measured at 1,300mm (1.3m).

Figure 35 shows the percentage of legal and juvenile Barramundi measured each year from 2009-2012. In 2009 66.8% of all fish measured were legal while in 2012 it was 55.5%. This was likely to be from a combination of high exploitation rates each year and an increased number of recruits being caught.

17. BARRAMUNDI RECRUITMENT

Recruitment refers to juvenile fish that "recruit" to the fishery when they reach legal size. Good recruitment occurs when there is good spawning, generally from October - January, followed by above wet season flows that juvenile Barramundi use to access freshwater, which is a preferred habitat for these smaller fish15.

Juvenile Barramundi are caught in estuaries in throw nets while chasing bait and on rod and line using small baits or lures. An electrofishing survey was undertaken by NT Fisheries to assess recruitment in the freshwater reaches of the McArthur River (see section 16). Lengths of juvenile fish were recorded to assess recruitment however it was not possible to get accurate lengths from many of the fish caught in throw nets.

Barramundi are fast growing with fish generally reaching 200-350mm in their first year and 400-550mm in their second year. During the third year most fish will have reached legal size16.

River flow data were obtained for the McArthur River at monitoring station G9070121 at Borroloola17 from 2005 to 2012. Figure 36 shows river flows compared to the length of fish over time.

Figure 37 shows the juvenile Barramundi recorded to date with the lengths of fish over time. The arrows are indicative of recruits from the past 4 years growing over time. This indicates recruitment occurred in each of the years. There were insufficient data to draw any conclusions on the level of recruitment each year and how that might be influenced by river flows however it does suggest that 2011 was a slightly better recruitment year following the largest flows for the past 8 years.

15 "Does the quantity and timing of fresh water flowing into a dry tropical estuary affect year-class strength of Barramundi" Jonathan Staunton-Smith et al, Marine and Freshwater Research 2004:55, 787-797 and "Effects of Local Climate on Recreational Fisheries in Central Queensland Australia: A guide to the impacts of climate change" W Sawynok and J Platten (in press) 16 "Age and Growth Studies of Barramundi, Lates calcarifer (Bloch), in Northern Australia" TLO Davis and GP Kirkwood, Marine and Freshwater Research 1984:35, 673-689 17 River flow data obtained from the Department of Natural Resources, Environment, the Arts and Sport

McArthur River Monitoring page 43 1400 1200 TL KING ASH BAY BARRAMUNDI Flow (GL) 1100 1200 1000

900 1000 800 ) legal length ) m L

m 700 G

( 800 (

h w t o g

600 l f n

r e l e 600 v

h 500 i s i R F 400 400 300

200 200 100

0 0 4 5 6 7 8 9 0 1 2 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 / / / / / / / / / 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 / / / / / / / / / 9 9 9 9 8 8 8 8 7 Date

Figure 36: River flows in the McArthur River and lengths of Barramundi over time

BARRAMUNDI RECRUITMENT

600

500

400 ) m m (

H 300 T G N E L 200

100 2009 2010 2011 2012

0 18-Dec-08 06-Jul-09 22-Jan-10 10-Aug-10 26-Feb-11 14-Sep-11 01-Apr-12 18-Oct-12

Figure 37: Lengths of Barramundi over time showing recruits for the last 4 years (arrows indicate growth of year class recruits over time)

McArthur River Monitoring page 44 Figure 38: Locating small juvenile Barramundi is an important part of understanding recruitment

A number of juvenile Barramundi of less that 200mm (figure 38) have been reported caught in throw nets in the estuaries however no accurate measurements of the lengths of these fish were available. It is important in understanding recruitment that habitats used by these smaller fish are identified.

18. ELECTROFISHING SURVEYS

Electrofishing surveys were undertaken by NT Fisheries in 2010 and 2012 to provide additional data on recruitment. The surveys were carried out in the freshwater section of the McArthur River near Borroloola, both upstream and downstream from the Borroloola crossing on the Carpentaria Highway (figure 39). The surveys were carried out using standard protocols and most Barramundi captured were tagged and released.

In the November 2010 survey a total of 79 Barramundi were tagged. There were also 2 recaptures of fish that were tagged during the survey and 2 were recaptures of fish tagged as part of the McArthur River Mine monitoring program by Indo-Pacific Environmental Pty Ltd (IPE).

Figure 40 shows the size range of fish tagged during the 2010 survey with most fish being 2010 and 2009 recruits and smaller numbers of larger fish. Recruits from those 2 years comprise 77.2% of the fish electrofished.

In the July 2012 survey a total of 42 Barramundi were tagged and a further 9 smaller fish measured and released. There were also 4 recaptures of fish that were tagged as part of this project and 1 recapture was of a fish tagged as part of the McArthur River Mine monitoring program by IPE.

McArthur River Monitoring page 45 l e n n a h C el n nn to a g Ch in e rr ri a u Warren Inlet C C Ba tte reek n Dugong C Cr r ee ive k R ur Rutherford Creek rth cA M Chadwick Creek

k King ree n C Ash tte Jo Ba hn Bay so n R iv er er iv r R e ur h th tc Ar le c F M e h T

r e iv R

r u h t r A c Borroloola M BOR S15 MAB J1 MAB K1

Figure 39: Site of NT electrofishing surveys on the McArthur River at Borroloola in 2010 and 2012

Figure 41 shows the size range of fish tagged and recaptured during the 2012 survey with most fish being 2012 and 2011 recruits and smaller numbers of larger fish. Recruits from those 2 years comprise 57.9% of the fish electrofished.

While the electrofishing surveys indicated a level of recruitment each year from 2009-12 there were insufficient data to estimate the relative strengths of recruitment each year.

20 ELECTROFISHED BARRAMUNDI NOV 2010 18 2010 recruits 16 2009 recruits 14 H S I

F 12

F O 10 R E B

M 8 U N 6

0 250: 300: 350: 400: 450: 500: 550: 600: 650: 700: 750: 800: 299 349 399 449 499 549 599 649 699 749 799 849 LENGTH (mm)

Figure 40: Size range of fish tagged during the 2010 electrofishing survey

McArthur River Monitoring page 46 12

ELECTROFISHED BARRAMUNDI JUL 2012 2012 2011 10 recruits recruits

8 H S I F

F O 6 R E B M U

N 4

0 150:199 200:249 250: 300: 350: 400: 450: 500: 550: 600: 650: 700: 750: 800: 299 349 399 449 499 549 599 649 699 749 799 849 LENGTH (mm)

Figure 41: Size range of Barramundi tagged and recaptured during the 2012 survey

19. GOLDEN SNAPPER TAGGING

The project objectives were reviewed in 2011 and tagging of Golden Snapper was included based on concerns raised for their stocks and to support tagging of Golden Snapper in other parts of the Northern Territory, particularly around Darwin. Tagging of Golden Snapper commenced in Oct 2011. When collecting trip details fishers provided details of Golden Snapper measured so that a size profile was able to be determined.

There were 203 fish tagged and no recaptures have been reported to date. Figure 42 shows a typical tagged Golden Snapper from the area. Most fish were tagged in depths of less than 5m so barotrauma was not considered to be an issue.

Figure 42: Typical Golden Snapper tagged around Centre Island

McArthur River Monitoring page 47 Figure 43: Locations where Golden Snapper have been tagged

Figure 43 shows the locations where Golden Snapper have been tagged. This shows that most Golden Snapper are tagged in the lower reaches of estuaries and around the islands however more data are required to complete the profile of habitats used by Golden Snapper. There were 38 grids where Golden Snapper were tagged. The most fish were tagged in grid U3 on map KAB (Centre Island) with 42 and grid K3 on map KAB (Davies Channel) with 22.

There were 944 Golden Snapper measured. Figure 44 shows the size ranges of fish that have been measured. Of the fish measured 689 (73.0%) were from 350:499mm in length. The longest fish measured was 770mm and it was kept with a fish of 755mm tagged.

Figure 45 shows the Golden Snapper that were measured and kept. The largest numbers of fish kept (42.2%) were from 400:449mm in length.

McArthur River Monitoring page 48 300

GOLDEN SNAPPER SIZES 250 Tagged Measured

H 200 S I F

F O 150 R E B M U

N 100

0 9 9 9 9 9 9 9 9 9 9 9 9 4 9 4 9 4 9 4 9 4 9 4 9 2 2 3 3 4 4 5 5 6 6 7 7

: : : : : : : : : : : : 0 0 0 0 0 0 0 0 0 0 0 0 0 5 0 5 0 5 0 5 0 5 0 5 2 2 3 3 4 4 5 5 6 6 7 7

SIZE RANGE (MM)

Figure 44: Sizes of measured Golden Snapper

200 LENGTHS OF GOLDEN SNAPPER KEPT 180

160

140 H S

I 120 F

F O 100 R E B

M 80 U N

0 9 9 9 9 9 9 9 9 9 9 9 4 9 4 9 4 9 4 9 4 9 9 2 2 3 3 4 4 5 5 6 6 7

: : : : : : : : : : : 0 0 0 0 0 0 0 0 0 0 0 0 5 0 5 0 5 0 5 0 5 5 2 2 3 3 4 4 5 5 6 6 7

SIZE RANGE (MM)

Figure 45 : Sizes of Golden Snapper measured and kept

McArthur River Monitoring page 49 20. COMPARISON WITH OTHER RIVER SYSTEMS

The project has focused on developing an understanding of fish stocks, particularly Barramundi in the McArthur River system. To understand the status of the stock it is necessary to compare the results for the McArthur River with other rivers system. A number of other river systems that support Barramundi that have comparable data were selected for comparison. These were:

 Daly River in the Northern Territory18  Rivers at Weipa that run into Albatross Bay on Cape York19  Fitzroy River at Rockhampton on the east coast of Queensland20

The Daly River is one of the most important Barramundi fisheries in the Northern Territory with recreational fishing only in the river. Data for the Daly River has been obtained from fish tagged during the Barra Classic and Barra National fishing competitions.

A number of rivers run into Albatross Bay at Weipa with the main ones being Mission River, Hey River, Embley River and Pine River. This is an important Barramundi fishery supporting both recreational and commercial fishing. Fishing effort is likely to be less than on the McArthur River.

The Fitzroy River at Rockhampton on the east coast of Queensland is an important Barramundi fishery supporting both recreational and commercial fishing and is heavily fished. The river has a large delta system similar to the McArthur.

Tag and recapture data were examined for the same period as this project with the number of fish tagged, number recaptured and the recapture rates were compared for 2009-12. Figure 46 shows the recapture rates for the 4 river systems with the rate for the McArthur River significantly lower than for the Daly and Fitzroy Rivers, however if is higher than for the Weipa rivers.

20% BARRAMUNDI RECAPTURE RATES FOR RIVERS 18% 15.4% 16%

14%

12%

10% 7.1% 8%

4% 1.9% 2% 0.8%

0% McArthur Daly Weipa Fitzroy

Figure 46: Comparison of recapture rates from 4 river systems

18 Data for Day River from NT Fisheries 19 Data for Weipa from Suntag database 20 Data on the Fitzroy River from Suntag database

McArthur River Monitoring page 50 The exploitation rates for the Daly, McArthur and Weipa rivers were also compared from 1991- 2012 as shown in figure 47. This shows that the exploitation rates for the McArthur River are less than for the Daly and Fitzroy Rivers. The exploitation rates are likely to be higher than shown due to the non reporting of recaptures.

12.0% COMPARISON OF EXPLOITATION RATES

10.0%

DALY E

T 8.0% MCARTHUR A R

FITZROY N O I

T 6.0% A T I O L P 4.0% X E

2.0%

0.0% 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 9 9 9 9 9 9 9 9 9 9 0 0 0 0 0 0 0 0 0 0 1 1 1 9 9 9 9 9 9 9 9 9 9 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 YEAR

Figure 47: Exploitation rates for the Daly, McArthur and Fitzroy rivers

Figure 48 shows a comparison of Barramundi lengths for fish measured in 2011 for the McArthur, Fitzroy and Weipa rivers. This shows that average fish size that year was the greatest for the McArthur River and the least for the Weipa rivers.

1400 COMPARISONS OF BARRAMUNDI LENGTHS 1200 McArthur 1000 Weipa H S

I Fitzroy F

F 800 O

R E

B 600 M U N 400

200

0 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0

1 1 : : : : : : : : : : : : : : : : : : : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 1 1 SIZE RANGE (MM)

Figure 48: Comparison of Barramundi lengths for the McArthur, Fitzroy and Weipa Rivers for fish measured in 2011

McArthur River Monitoring page 51 21. DISCUSSION

Estimating Fishing Effort

Estimating fishing effort was complex because of the varying ways in which fishing was undertaken. Trailer counts at the KAB ramp were reasonably straight forward and there were sufficient days when trailer counts were made to provide a reliable estimate of fishing trips from the ramp. Counts at the other ramps were only made infrequently however the use of these ramps was low compared with the KAB ramp and the estimates of trips from these ramps are considered to reasonably reflect their use.

Estimating the number of trips from moored boats was more difficult as there were boats moored all the way from Genny Flats to Batten Point, a distance of around 9km. Trailers for moored boats were taken back to the residence or campsite and did not show up in the counts of trailers at the ramp. Unlike trailers at the ramp, which indicated a fishing trip, those who moored their boats did not go fishing every day. Some residents with moored boat only went fishing intermittently. Based on observation and discussions with residents and visitors it was considered that an estimate of half the moored boats going fishing each day was realistic.

The estimate of fishing effort from houseboats was the least reliable. Houseboats were used a base close to locations that were fished in the McArthur River and Crooked Creek. Houseboats generally had 2-6 boats moored alongside which were then used to go fishing. It was not unusual for several "trips" to be made from the houseboat each day with boats often fishing early in the morning and then returning to the houseboat for breakfast or a break during the hottest part of the day. To estimate the number of trips from houseboats it was assumed that each boat made a trip each day, even if that was broken by a return to the houseboat. This made the trip comparable to those using the boat ramp. Given the short hiring period of houseboats, generally less than a week or two it was assumed that the boats associated with the houseboats went fishing each day and that each boat had 2 fishers.

Data were obtained for 4 of the 6 houseboats in 2010 and that provided the basis for estimating the number of trips from houseboats. Data from 2011 and 2012 was to be made available however had not been received by the time this report was prepared. In the absence of additional data on houseboat use estimates were made for each of the other years based on 2010 and visitor data. This reduced the reliability of the estimates and the error margin is likely to be 10-20%.

The estimate of landbased trips was very difficult due to the number of access points where fishing could be undertaken. Many of the visiting fishers had access to the river bank from Genny Flats to Batten Point and often had a rod propped up on the bank and only attended it to check the bait or reel in a fish. The estimate of landbased trips was based on discussions with residents and visiting fishers and need to be treated with caution. However these "trips" had very low catch rates and did not significant influence the overall estimate of catch rates. Other landbased trips were undertaken around Borroloola, mainly be local residents.

Estimating Catch

Catch details were obtained from boat ramp surveys or by interview with fishers after their trip. While many fishers were willing to provide their catch details a small percentage (less than 5%) were evasive and did not provide catch details. Some of the evasiveness was based on wanting to keep their catch details and fishing location to themselves while there was also an element that was likely to have fished outside the regulations.

While catch rates for Barramundi were low for individual trips many fishers keep Barramundi over several trips until they reached their possession limit. This was particularly so for houseboat fishers and for fishers visiting just after the end of the wet season and in late

McArthur River Monitoring page 52 spring. Spring in each of the 3 years produced the highest catch rates for Barramundi as this is the time when the more experienced fishers visit the area to go fishing.

Because of the uncertainty in estimating fishing effort, particularly for houseboats, the estimate of annual catch of Barramundi should be treated with caution and has been provided as an indicative estimate only. However it is likely that the recreational catch in the McArthur River exceeds the commercial catch in the area from the Robinson River to Bing Bong, including the islands. It should be noted that estimate of catch does not include the Wearyan River.

Barramundi Growth

The number of recaptures where growth data were available was low and more data are needed. However the available data suggests that growth is very variable. The average growth of 85+65mm is lower than in most other areas. However this low average growth rate is influenced by 30.6% of the fish having a growth rate of less than 40mm/year or less than half the average growth.

Genetic samples were collected from the project area for a James Cook University project21 re- examining the genetics of Barramundi throughout Australia. The results of this study will be available in 2013 and may provide information that could shed some light on growth rates being observed.

Barramundi Movement

Recaptures of tagged fish indicate that most fish remain within the river system. However there have been a number of fish that have moved between waterways. This was particularly noted for fish tagged near the mouth of waterways. Many Barramundi use the mangrove fringes lining the Gulf between waterways and there are no impediments that inhibit movement along these fringes.

There were 2 fish tagged in the Calvert River as part of the North Australia Freshwater Fish project that were recaptured in the project area. One fish was recaptured at the mouth of the McArthur River while the other was recaptured at the mouth of the Wearyan River. Both fish had moved westward over 200km. There is a view among local fishers that there is a westward movement of Barramundi in the Gulf. More recaptures are needed before this can be confirmed.

Barramundi Recruitment

There was a level of recruitment in the area each year with perhaps a boost in 2011. This followed the largest flow in the river since 2005. Unlike many other NT rivers the McArthur River does not have extensive freshwater wetlands that can act as nursery areas. This limits the area available to juvenile fish to the main waterways where they are likely to be subject to increased levels of predation and competition.

Juvenile fish from 300-550mm were located throughout the system in areas inhabited by adult fish. Many fishers reported catching Barramundi from around 250-400mm in their throw nets, particularly at the mouths of drains. However fewer fish below 250mm were recorded. A small number were recorded in the electrofishing survey in 2012 at the Carpentaria Highway crossing at Borroloola. There were few reports of these smaller fish caught in throw nets that could be verified.

21 Barramundi Genetics Audit - Carolyn Smith-Keune Centre for Sustainable Tropical Fisheries and Aquaculture James Cook University

McArthur River Monitoring page 53 22. CONCLUSIONS

The status of the fishing effort and stocks can be summarised as:

McArthur River Monitoring page 54 23. APPENDIX 1

Figure 49 shows the trip form used to collect details of fishing trips in the McArthur River.

Figure 49: McArthur fishing trip data form

McArthur River Monitoring page 55 24. APPENDIX 2

Figure 50 shows the tidal predictions for Centre Island for Nov 2012.22

Figure 50: Typical monthly tidal cycle for Centre Island (Nov 2012)

22 From Bureau of Meteorology 2010

McArthur River Monitoring page 56